Cirsium hydrophilum (Greene) Jeps.
Family: Asteraceae
Suisun Thistle
Cirsium hydrophilum image
Doug Wirtz  

Biennials or monocarpic perennials, 100-220 cm; taprooted. Stems 1-several, erect, (hollow), openly branched distally or throughout, thinly arachnoid with fine, non-septate trichomes, glabrate. Leaves: blades elliptic to broadly oblanceolate, 10-40+ cm, pinnatifid 1/2-2/3 distance to midveins, larger usually with broad sinuses, lobes broad, few lobed or dentate, main spines 2-9 mm, abaxial faces ± gray-tomentose, sometimes ± glabrate, adaxial thinly arachnoid-tomentose, soon glabrescent; basal present or withered at flowering, winged-petiolate; principal cauline sessile, progressively reduced distally, bases auriculate-clasping or shortly decurrent; distal cauline reduced, bractlike, often spinier than proximal. Heads borne singly or few at branch tips, sometimes subtended by clustered, ± leafy bracts, collectively forming ± open, many-headed paniculiform arrays. Peduncles 0-10+ cm. Involucres ovoid to campanulate, 1.5-2.5 × 1.5-3 cm, thinly arachnoid, glabrate. Phyllaries in 6-9 series, imbricate, dark green to brownish, lanceolate (outer) to linear (inner), abaxial faces with narrow glutinous ridge; outer and middle appressed, apices spreading, finely serrulate, spines slender, 1-2 mm; apices of inner erect, ± flexuous. Corollas pale rose-purple, 18-23 mm, tubes 8-10 mm, throats 5-6 mm, lobes 5-7 mm; style tips 3.5-4.5 mm. Cypselae dark brown to black, 4-5 mm, collars very narrow, stramineous; pappi ca. 15 mm. 2n = 32.

Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz  
Cirsium hydrophilum image
Doug Wirtz